FIX: Remove optional context in parser

The context was optional because I thought that paring an RC formula
did not need context.

You at least need the sheet in which you are parsing
For instance toknow if a defined name is local

xlsx/src/import/worksheets.rs

@@ -309,7 +309,7 @@ fn from_a1_to_rc(
     let mut parser = Parser::new(worksheets.to_owned(), defined_names, tables);
     let cell_reference =
         parse_reference(&context).map_err(|error| XlsxError::Xml(error.to_string()))?;
-    let t = parser.parse(&formula, &Some(cell_reference));
+    let t = parser.parse(&formula, &cell_reference);
     Ok(to_rc_format(&t))
 }